The main GP day is Sunday in Brno and tickets can be bought by foreigners on the internet. I've been before a few times and have always had a friend locally buy them.
Getting back to UK on Monday is a thrash as it's the best part of 800 miles if you take the most quickest and most motorwayed route through East Germany
The circuit is just off the motorway to the west of the city and is built in some quite deep woods. What sort of accommodation are yo ulooking at and how close to the ttrack/city do you want to be?
I can recommend several places to stay and these will need booking in advance as they book out very easily. There are campsites dotted all around the track and these are former Sokol association (sort of athletics/fitness clubs) places usually. Never been into wooden huts myself.
I can get some addresses and numbers for you. I used to teach locally and have many contacts in Brno and am going to a local bike rally over Spring Bank Holiday.
If you like reasonable B&B I can recommend
Na Ruzku
in Ricany. A long walk to the track but better to ride the 3 or 4 miles! Good clean accommodation -
http://www.almara.cz/naruzku/. I have stayed here myself and it very good and quite cheap by UK standards....
Or Hotel Admiral
(
http://www.hotela.cz/ricany/index_de.htm)
also in Ricany email is
info@hotela.cz they are slow but do answer in English eventually although the website is in Czech or German. Not actually stayed at this one but have heard some good things about it.
A third I can recommend although it's a little less glitzy is Pod Horkou in a village called Chudcice about 8 miles from the motorway and GP circuit..., this is where the Czech Suzuki Owners Club have been having hteir annual rally since at least 1990 (first one I went to!) and I guess before. Small place so it depends on your group, and about 300kc a night per person.... 43kc or so to the £1!
Brno itself has lots of things to have alook at in a days sightseeing, have a look at the web for english webpages or try the Lonely Planet book on the Czech Republic.
As for getitng there. I usually slog over on the motorway either taking the northern route from Koln on the A4 across to Chemnitz, then down to Prague or the more southern route via A3 and A6 from Koln to Nurnberg, then a secion of B14 to Waidhaus and then m-way to Prague and Brno.
A far longer route via Austria is possible if you really like motorways!